Disclosed are intermediate transfer members, and more specifically, intermediate transfer members useful in transferring a developed image in an electrostatographic, for example xerographic, including digital, image on image, and the like, machines or apparatuses and printers. In embodiments, there are selected intermediate transfer members comprised of a first polyimide layer and a second polyetherimide-b-polysiloxane layer, and more specifically, where the economical polyetherimide-b-polysiloxane layer is in full contact with the polyimide layer and where there can be included in at least one of the first and second layers a conductive component. A number of advantages are associated with the intermediate transfer members of the present disclosure, such as excellent mechanical characteristics, robustness, consistent, and excellent surface resistivities, and acceptable adhesion properties, especially when there is included in the intermediate transfer member an adhesive layer; excellent maintained conductivity or resistivity for extended time periods; dimensional stability; ITB humidity insensitivity for extended time periods; excellent dispersability in a polymeric solution; low and acceptable surface friction characteristics; and minimum or substantially no peeling or separation of the layers.
One specific advantage of the disclosed two-layer ITB is its low surface energy, for example, a contact angle of about 100° (degrees) for the block copolymer as compared to about 50° for the polyimide layer, which advantage is of value with regard to improved toner transfer and cleaning, where in embodiments the top layer functions primarily to obtain high fidelity transfer in view of its low surface energy, while the base polyimide layer provides reliable mechanical strength.
In aspects thereof, the present disclosure relates to a multi-layer intermediate transfer layer, such as a belt (ITB) comprised of a polyimide base layer and a polyetherimide-b-polysiloxane block copolymer top layer, and where each layer further includes a conductive component, and an optional adhesive layer situated between the two layers, and which layered member can be prepared by known solution casting methods and known extrusion molded processes with the optional adhesive layer can be generated and applied by known spray coating and flow coating processes.
Furthermore, disclosed herein is a hydrophobic intermediate transfer member having a surface resistivity of from about 107 to about 1014 ohm/sq, or from about 109 to about 1012 ohm/sq, and a bulk resistivity of from about 107 to about 1014 ohm/sq, or from about 109 to about 1012 ohm cm.
The ITB member comprised of the disclosed hydrophobic polyetherimide-b-polysiloxane block copolymer is, for example, hydrophobic, such as an about 50 percent more hydrophobic as determined by an about 50° higher contact angle as compared to an ITB that does not contain the polyetherimide-b-polysiloxane block copolymer. In addition, primarily because of the ITB water repelling properties determined, for example, by accelerated aging experiments at 80° F./80 percent humidity, for four weeks, the surface resistivity of the disclosed hydrophobic ITB member remained unchanged, while that of the a similar comparative member which is free of the polyetherimide-b-polysiloxane varied.
In a typical electrostatographic reproducing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member, and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles and colorant. Generally, the electrostatic latent image is developed by contacting it with a developer mixture comprised of a dry developer mixture, which usually comprises carrier granules having toner particles adhering triboelectrically thereto, or a liquid developer material, which may include a liquid carrier having toner particles dispersed therein. The developer material is advanced into contact with the electrostatic latent image, and the toner particles are deposited thereon in image configuration. Subsequently, the developed image is transferred to a copy sheet. It is advantageous to transfer the developed image to a coated intermediate transfer web, belt or component, and subsequently transfer with a high transfer efficiency the developed image from the intermediate transfer member to a permanent substrate. The toner image is subsequently usually fixed or fused upon a support, which may be the photosensitive member itself, or other support sheet such as plain paper.
In electrostatographic printing machines wherein the toner image is electrostatically transferred by a potential difference between the imaging member and the intermediate transfer member, the transfer of the toner particles to the intermediate transfer member, and the retention thereof should be substantially complete so that the image ultimately transferred to the image receiving substrate will have a high resolution. Substantially about 100 percent toner transfer occurs when most or all of the toner particles comprising the image are transferred, and little residual toner remains on the surface from which the image was transferred.
Intermediate transfer members possess a number of advantages, such as enabling high throughput at modest process speeds; improving registration of the final color toner image in color systems using synchronous development of one or more component colors, and using one or more transfer stations; and increasing the number of substrates that can be selected. However, a disadvantage of using an intermediate transfer member is that a plurality of transfer operations is usually needed allowing for the possibility of charge exchange occurring between toner particles, and the transfer member which ultimately can lead to less than complete toner transfer, resulting in low resolution images on the image receiving substrate, and image deterioration. When the image is in color, the image can additionally suffer from color shifting and color deterioration.
Attempts at controlling the resistivity of intermediate transfer members by, for example, adding conductive fillers, such as ionic additives and/or carbon black to the outer layer, are disclosed in U.S. Pat. No. 6,397,034 which describes the use of fluorinated carbon filler in a polyimide intermediate transfer member layer. However, there can be problems associated with the use of such fillers in that undissolved particles frequently bloom or migrate to the surface of the fluorinated polymer and cause imperfections to the polymer, thereby causing nonuniform resistivity, which in turn causes poor antistatic properties and poor mechanical strength characteristics. Also, ionic additives on the ITB surface may interfere with toner release. Furthermore, bubbles may appear in the polymer, some of which can only be seen with the aid of a microscope, and others of which are large enough to be observed with the naked eye resulting in poor or nonuniform electrical properties and poor mechanical properties.
In addition, the ionic additives themselves are sensitive to changes in temperature, humidity, and operating time. These sensitivities often limit the resistivity range. For example, the resistivity usually decreases by up to two orders of magnitude or more as the humidity increases from about 20 percent to 80 percent relative humidity. This effect limits the operational or process latitude.
Moreover, ion transfer can also occur in these systems. The transfer of ions leads to charge exchanges and insufficient transfers, which in turn causes low image resolution and image deterioration, thereby adversely affecting the copy quality. In color systems, additional adverse results include color shifting and color deterioration. Ion transfer also increases the resistivity of the polymer member after repetitive use. This can limit the process and operational latitude, and eventually the ion filled polymer member will be unusable.
Therefore, it is desired to provide an intermediate transfer member with a number of the advantages illustrated herein such as excellent mechanical, and humidity insensitivity characteristics permitting high copy quality where developed images with minimal resolution issues can obtained. It is also desired to provide a weldable intermediate transfer belt that may not, but could, have puzzle cut seams, and instead, has a weldable seam, thereby providing a belt that can be manufactured without labor intensive steps, such as manually piecing together the puzzle cut seam with fingers, and without the lengthy high temperature and high humidity conditioning steps.
A number of the known ITB formulations apply carbon black or polyaniline as the conductive species, however, this has some limitations. For example, polyaniline is readily oxidized and results in loss of conductivity, its thermal stability is usually limited to about 200° C., and it begins to lose its conductivity at above 200° C. Also, it can be difficult to prepare carbon black based ITBs with consistent resistivity because the required loadings reside on the vertical part of the percolation curve. The amount of carbon black and how carbon black is processed (primary particle size and aggregate size) are of value for conductivity and for the manufacturing of intermediate belts.